After the manufacture of products, i.e., components, it is usually necessary before using them to clean them of dirt particles using an appropriate cleaning process. In the context of quality control, the performance of the available cleaning processes is usually checked using light-microscopy systems.
For this purpose, a product, i.e., a component, which was cleaned in accordance with the available cleaning process, is once again thoroughly cleaned, the dirt particles that are removed in the process remaining, for example, in a cleaning fluid, which is passed through a filter. In this context, the dirt particles remain on the filter, which is placed under a light-optical microscope of the light-microscopy system. Using the light-microscopy system, the loaded filter is analyzed, the light-optical microscope being connected to an image analysis system, i.e., evaluation system. In the evaluation, bright and dark spots are distinguished and their size and number is determined. Then a classification takes place of the dark spots, which represent the dirt particles.
However, in this context, it is disadvantageous that the received evaluation protocols of the image analysis systems that are known from practice currently cannot be verified, because the precise actual accumulation on the filter, i.e., the number of dirt particles of different particle size categories, is not known and is difficult to determine using manual evaluation. Therefore, it is impossible to determine the deviation between the evaluation protocol and the actual accumulation.
From practice, test pieces, i.e., so-called standards, are known, which are covered by a single geometrical pattern. This single pattern, whose dimensions are known, is measured and classified in one single measuring step using an optoelectronic image analysis system.
However, using test pieces of this type, only individual measurements can be carried out, which is a disadvantage, whereas using an image analysis system a totality of actual filters that are loaded with dirt particles can be evaluated such that a classification of the dirt particles is produced with respect to size and number, on the basis of which it is possible to carry out an evaluation of a cleaning process that has been applied.
Filters having dirt particles are evaluated using known optoelectronic image analysis systems, such that the loaded filter surface is divided into different measuring fields, i.e., test surfaces, which are scanned by the image analysis system sequentially. After termination of the automatic test run, the different individual measurements are combined, and an evaluation for the entire filter surface is created. Using the test pieces that are known from practice, this kind of automatic measuring run of an optoelectronic image analysis system cannot be simulated, because the test pieces are covered by only a single geometrical pattern, or they have geometrical patterns that are nested in each other and that cannot be resolved by the image analysis systems.
In an automatic measuring run, the filter element may be typically divided into a plurality of measuring fields, which are scanned, measured, and then analyzed in sequence by an optoelectronic image analysis system. One particularly problematic case occurs when a particle is bisected, i.e., partially located in one measuring field and partially in one or more other measuring fields. Then, the automatic measuring run should resolve the particle as one single particle and assign it to only one measuring field. Otherwise, errors in the analysis can occur either over-counting or under-counting the particle. This is undesirable, because the evaluation of the number and size of particles is used to determine the quality of the cleaning process and, in response to the erroneous detection of a high level of impurities of particles of a specific size category, the evaluation can lead to inappropriate measures being taken for improving the cleaning process.
Another method of preparing a test piece for evaluation of an image analysis system is to arrange actual dirt particles on a substrate and to localize them in an embedding mass that constitutes a solid connection to the substrate. However, in this context, it is disadvantageous that the known embedding masses are not durable and that the arrangement of the particles does not stay unchanged, so that test pieces of this type become unusable as their service life proceeds. A further disadvantage lies in the fact that the dimensions of the dirt particles used have to be determined manually in order to be able to analyze the evaluation of an optoelectronic image analysis system, standards of this type representing unique specimens, which can only be reproduced with great difficulty, if at all.